nullish

Transforms a potentially null/undefined value into an Either. Allows propagating presence/absence in a type-safe way.

Interactive example

Syntax

function nullish<const GenericInput extends unknown = undefined>(
  input: GenericInput
): GenericInput extends NullishValue
  ? EitherNullishEmpty<GenericInput>
  : EitherNullishFilled<GenericInput>;

Parameters

• input: Value to wrap (null, undefined, or any other value).

Return value

• EitherNullishFilled when the value exists.
• EitherNullishEmpty when the value is null or undefined.

See also

• nullishEmpty.
• nullishFilled.
• whenIsNullishFilled.